# Simple gear train with two gears (Torque ratio)

## Description

The gear ratio of a gear train, also known as its speed ratio, is the ratio of the angular velocity of the input gear to the angular velocity of the output gear. The gear ratio can be calculated directly from the numbers of teeth on the gears in the gear train. The simplest example of a gear train has two gears. The “input gear” (a.k.a. the drive gear) transmits power to the “output gear” (a.k.a. the driven gear). A gear train can be analyzed using the principle of virtual work to show that its torque ratio, which is the ratio of its output torque to its input torque, is equal to the gear ratio, or speed ratio, of the gear train. (The torque ratio of a gear train is also known as its mechanical advantage)

Related formulas## Variables

N_{B} | The number of teeth on the output gear (dimensionless) |

N_{A} | The number of teeth on the input gear (dimensionless) |

T_{B} | The output torque (N*m) |

T_{A} | The input torque (N*m) |